1. Field of the Invention
This invention relates to asphalt additive compositions and more particularly to asphalt additive compositions comprising (A) an asphalt-soluble, metallic organic strength improving compound, either alone, or in combination with other metallic organic compounds and (B) an anti-strip compound wherein said anti-strip compound is present in a concentration of at least 10 weight percent. The asphalt additive compositions are useful, particularly in preparing improved asphalt concrete compositions with improved water resistance and strength improvement.
The term "asphalt" or "asphalt cement" as used in the description of the present application refers to any of a variety of solid or semi-solid materials at room temperature which gradually liquify when heated, and in which the predominant constituents are naturally occurring bitumens of which are obtained as residue in petroleum refining. Asphalt is further defined by Kirk-othmer, Encyclopedia of Chemical Technology, Vol. 3, Third Ed. (1978) pp. 284-327, John Wiley & Sons, New York. An additional discussion appears in the publication entitled "A Brief Introduction to Asphalt and some of its Uses", Manual Series No. 5 (MS-5), The Asphalt Institute, 7th Ed., Sept., 1974. Both of these references are hereby incorporated by reference.
Asphalt cements have found particular utility when combined with aggregates. Such combinations, generally referred to as "asphalt concrete", are employed extensively as paving compositions for roads, driveways, parking lots, airport runways, etc. The asphalt is converted to a fluid state when paving a road. One fluid form is the suspension or emulsion of the asphalt in water. After spreading and compressing the aggregate-containing asphalt, water evaporates or separates, and the asphalt hardens into a continuous mass. Another form of asphalt employed in road construction is a cutback, i.e., a liquid petroleum product produced by fluxing an asphaltic base with a suitable organic solvent or distillate. A road is formed by paving the aggregate-containing cutback and evaporating the volatile distillate from the mass. An advantage of using the above road construction techniques is the avoidance of high temperature application. In an alternative and most widely used technique, the asphalt and aggregate can be mixed and applied at elevated temperatures at the fluid state of the asphalt to form the road. This form of asphalt, which is neither cut-back nor emulsified generally is referred to as asphalt cement.
2. Description of the Related Art
U.S. Pat. No. 4,410,367 (LeGrand, Oct. 18, 1983) describes a method for enhancing the resistance of aggregate to the effects of atmospheric degradation and improve its ability to resist separation from cured asphalt concrete when incorporated into asphalt cement prior to cure to reinforce the resulting asphalt concrete mixture. This mixture is achieved by treating the aggregate with an aqueous polyelectrolyte surfactant and thereafter allowing the treated aggregate to dry by heating or exposure to ambient conditions.
U.S. Pat. No. 3,868,263 (McConnaughy, Feb. 25, 1975) is directed to a method of forming a paving composition in which an aggregate is mixed with a primary bituminous binder containing a bituminous material as an adhesion promoter to form a premix of binder coated aggregate. After the binder in the premix is cured the premix is mixed with a secondary bituminous binder to form a paving composition which can be stock piled or stored for later use without being subjected to deterioration as by rain or weathering.